Most current spaceflights adopt solar energy powered battery. A solar battery array can be installed either inside the spaceflight or outside in a form sail board. The solar-direction-detecting sail board batteries can provide more resource of electric power than batteries. In order to increase energy density out of a solar battery array, Hughes Aircraft Company has selected “soft folding solar batteries sail” (see, Space Station and Space Platform, pages 396-97). In order to deploy this kind of soft sail, the need of installing a solid holder and a limit of its size eventually becomes inevitable—energy density is not high enough (47 w/kg)—therefore the “soft coiling solar batteries sail” has not been widely selected.